Most of head and neck cancer patients will undergo radiotherapy. Xerostomia is probably its most frequent side effect. Subjective and objective criteria allow evaluating and grading xerostomia. New radiotherapy techniques and use of cytoprotectants can help to preserve salivary gland function. Parasym-pathicomimetics and saliva substitutes reduce symptoms. Strict mouth cleaning and fluoride's use prevent teeth deterioration and infections. Important breakthroughs have been made in the pathophysiology of xerostomia and new treatments are developed.